This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Neoadjuvant chemotherapy can achieve tumor downstaging and allow breast conservation in some patients. Response to chemotherapy is assessed clinically. Although this has been shown to be associated with improved disease-free survival, it is not clear whether clinical assessment of the primary tumor accurately reflects pathologic response. The UCSF Breast Center (N. Hylton and L. Esserman) are using MRI to assess changes in tumor size and distribution in response to neoadjuvant chemotherapy. Preliminary results indicate that tumor changes measured by MRI are better than clinical exam and are meaningful predictors of survival. The MRI signal origin is related to changes in blood volume fraction, perfusion, and spatial extent of the tumor site. These are precisely the functional parameters that the hand-held FDPM optical probe can provide in a single, non-invasive measurement. As a result, we will initiate a pilot study that examines 10 UCSF patients. Each patient will receive baseline MRI scans at UCSF, followed by optical scans at UCI. Subsequent MRI scans will be performed following each cycle of chemotherapy (AC, Adriamycin/Cyclophosphamide). In order to minimize the number of trips to Irvine, a second and final optical scan will be completed following the 4th AC cycle, just prior to surgery. Because optical and MRI provide complementary functional information, we believe these results will provide valuable insight into the mechanisms these therapies as well as help establish practical criteria for predicting drug efficacy